Other skies
Chinese Astronomy
In Chinese astronomy the sky is divided into the 二十八宿 (èrshíbā xiù), the 28 xiu or “lunar mansions”, and the 三垣 (sān yuán), the Three Enclosures. This page shows that system and calculates what can be calculated with the same engine as the rest of the site: the 24 solar terms of 2026, to the minute.
The 28 xiu
The xiu (宿, xiù) are 28 groups of stars near the ecliptic and the celestial equator. Each xiu is anchored by one star, its determinative star (距星, jùxīng). In our calculation a xiu runs from its determinative star to the determinative star of the next xiu, measured in right ascension; that is a choice for calculating, not a claim about where the ancient astronomers put the borders. The Moon passes through all 28 in one sidereal month, about 27.3 days.
The lists of determinative stars differ for four xiu: Xīn, Kuí, Zī and Shēn. We follow the list in the Chinese Wikipedia, the table “二十八宿及其距星” in the Chinese Wikipedia, which gives σ Scorpii for Xīn, ζ Andromedae for Kuí, φ¹ Orionis for Zī and δ Orionis for Shēn. The table in the English Wikipedia, which cites Sun Xiaochun (1997) and the International Dunhuang Project, gives α Scorpii, η Andromedae, λ Orionis and ζ Orionis. For the Moon this can decide which xiu it is in, and our calculators will say so when it does. We have not checked either list against Sun and Kistemaker, The Chinese Sky during the Han (1997).
In the Chinese list Zī follows Shēn so closely in right ascension that in our calculation it has no width, and the Moon there is counted in Shēn. The order of these two xiu is itself a known question: the Chinese Wikipedia describes a dispute in the Qing period, after which the traditional order was restored in 1752.
The four symbols
The 28 xiu are grouped by seven under the Four Symbols (四象, sì xiàng), each with a direction and a season: the Azure Dragon in the east (spring), the Vermilion Bird in the south (summer), the White Tiger in the west (autumn) and the Black Tortoise in the north (winter). The Chinese Wikipedia also writes 青龍 for the dragon.
Azure Dragon (蒼龍, Cānglóng): east, spring
| Xiu | Pinyin | English |
|---|---|---|
| 角 | Jiǎo | Horn |
| 亢 | Kàng | Neck |
| 氐 | Dī | Root |
| 房 | Fáng | Room |
| 心 | Xīn | Heart |
| 尾 | Wěi | Tail |
| 箕 | Jī | Winnowing-basket |
Vermilion Bird (朱雀, Zhūquè): south, summer
| Xiu | Pinyin | English |
|---|---|---|
| 井 | Jǐng | Well |
| 鬼 | Guǐ | Ghosts |
| 柳 | Liǔ | Willow |
| 星 | Xīng | Star |
| 張 / 张 | Zhāng | Extended net |
| 翼 | Yì | Wings |
| 軫 / 轸 | Zhěn | Chariot |
White Tiger (白虎, Báihǔ): west, autumn
| Xiu | Pinyin | English |
|---|---|---|
| 奎 | Kuí | Legs |
| 婁 / 娄 | Lóu | Bond |
| 胃 | Wèi | Stomach |
| 昴 | Mǎo | Hairy head |
| 畢 / 毕 | Bì | Net |
| 觜 | Zī | Turtle beak |
| 參 / 参 | Shēn | Three stars |
Black Tortoise (玄武, Xuánwǔ): north, winter
| Xiu | Pinyin | English |
|---|---|---|
| 斗 | Dǒu | Dipper |
| 牛 | Niú | Ox |
| 女 | Nǚ | Girl |
| 虛 / 虚 | Xū | Emptiness |
| 危 | Wēi | Rooftop |
| 室 | Shì | Encampment |
| 壁 | Bì | Wall |
Traditional characters; where the simplified form differs it follows after a slash.
The four palaces and their animals are old. The Huainanzi (chapter “Tianwen xun”) already pairs the four directions with a dragon (Cānglóng), a bird (Zhūniǎo), a tiger (Báihǔ) and a tortoise (Xuánwǔ), and the Shiji (chapter “Tianguan shu”) has the four palaces of the sky. The grouping of the 28 xiu under these four, after the three enclosures, is set out in the Butian ge, an astronomical poem attributed to Wang Ximing.
The Three Enclosures
Besides the 28 xiu the sky has three enclosures (三垣, sān yuán): Tàiwēi (太微垣), Zǐwēi (紫微垣) and Tiānshì (天市垣). Together with the 28 xiu they are called 三垣二十八宿. We do not draw the enclosures yet.
The names are old. The Shiji (“Tianguan shu”) already has the Purple Palace (Zǐgōng), the Tàiwēi and the Tiānshì, and the Huainanzi (“Tianwen xun”) the Purple Palace and the Tàiwēi. The Butian ge sets out the three enclosures and, after them, the 28 xiu in four groups. Its date is disputed (see below).
Needham describes Zǐwēi, the “Purple forbidden enclosure”, as the northern circumpolar region, a zone of some 15° radius around the pole, and Tàiwēi as the “Enclosure” of stars in Virgo, Coma Berenices and Leo.
The 24 solar terms of 2026
A solar term (節氣, jiéqì) is the moment the Sun passes a multiple of 15° of ecliptic longitude. We calculate the 24 of 2026 with Astronomy Engine, to the minute, in Beijing time (UTC+8), the time the Chinese calendar uses; where you live the date can differ by a day.
| Solar term | Sun at | Date and time in Beijing |
|---|---|---|
| 小寒 · Xiǎohán | 285° | January 5 at 16:23 |
| 大寒 · Dàhán | 300° | January 20 at 09:44 |
| 立春 · Lìchūn | 315° | February 4 at 04:01 |
| 雨水 · Yǔshuǐ | 330° | February 18 at 23:51 ‡ |
| 驚蟄 / 惊蛰 · Jīngzhé | 345° | March 5 at 21:58 |
| 春分 · Chūnfēn | 0° | March 20 at 22:45 |
| 清明 · Qīngmíng | 15° | April 5 at 02:39 |
| 穀雨 / 谷雨 · Gǔyǔ | 30° | April 20 at 09:39 |
| 立夏 · Lìxià | 45° | May 5 at 19:49 |
| 小滿 / 小满 · Xiǎomǎn | 60° | May 21 at 08:37 |
| 芒種 / 芒种 · Mángzhòng | 75° | June 5 at 23:48 ‡ |
| 夏至 · Xiàzhì | 90° | June 21 at 16:25 |
| 小暑 · Xiǎoshǔ | 105° | July 7 at 09:57 |
| 大暑 · Dàshǔ | 120° | July 23 at 03:13 |
| 立秋 · Lìqiū | 135° | August 7 at 19:42 |
| 處暑 / 处暑 · Chùshǔ | 150° | August 23 at 10:18 |
| 白露 · Báilù | 165° | September 7 at 22:41 |
| 秋分 · Qiūfēn | 180° | September 23 at 08:05 |
| 寒露 · Hánlù | 195° | October 8 at 14:29 |
| 霜降 · Shuāngjiàng | 210° | October 23 at 17:38 |
| 立冬 · Lìdōng | 225° | November 7 at 17:52 |
| 小雪 · Xiǎoxuě | 240° | November 22 at 15:23 |
| 大雪 · Dàxuě | 255° | December 7 at 10:52 |
| 冬至 · Dōngzhì | 270° | December 22 at 04:50 |
‡ The moment is within 15 minutes of midnight in Beijing; with another time convention the term falls on the next or the previous day.
Four moments from its history
Four moments from the history of Chinese astronomy, told only with what we could check in the sources themselves. Where the sources disagree, we say so; what we could not check is listed under “What we do not know”.
The Dunhuang star atlas
In 1907 the archaeologist Aurel Stein found, at the Silk Road town of Dunhuang, a paper scroll that is now in the British Library as Or.8210/S.3326. It opens with a text of omens drawn from clouds and the night sky (uranomancy) and then holds a star atlas: twelve maps of the sky and one map of the region around the pole. In their study of 2009 Jean-Marc Bonnet-Bidaud, Françoise Praderie and Susan Whitfield count 1,339 stars in 257 asterisms, drawn as colored dots. The maps show the 28 xiu and the three enclosures: Zǐwēi, Tàiwēi and Tiānshì.
The scroll carries no date. Needham proposed about the year 940; Ma Shichang (1983), from the clothing of a figure on the scroll and from taboo characters in the text, put it at about 705 to 710. Bonnet-Bidaud and his colleagues apply precession to the determinative stars of the xiu and to the position of the pole and find the years 649 to 684, in the early Tang, most probable. A possible author of the original is the astronomer Li Chunfeng (602–670), but there is no evidence that he ever went to Dunhuang; the atlas may have been made at the Imperial Observatory and brought there.
The authors call it “the oldest complete preserved star atlas known from any civilisation” and “the earliest known pictorial representation of the quasi-totality of Chinese constellations”. Their reason is that other ancient objects show constellation figures without individual stars, and that of the European works only the Farnese Globe, a Roman copy of a Greek original, is older. We give that as their claim, not as ours.
We show no image of the scroll: the terms of use of the International Dunhuang Project and the British Library, which hold the images, could not be checked.
The guest star of 1054
The Chinese history of the Song dynasty (Song shi) records in its astronomical treatise: 至和元年五月己丑，出天關東南，可數寸，歲餘稍沒。 In Duyvendak’s translation (1942): “In the 1st year of the period Chih-ho [1054], the 5th moon, the day chi-ch’ou [July 4] [a guest-star] appeared approximately several inches south-east of T’ien-kuan [ζ Tauri]. After more than a year it gradually became invisible.” The Chinese term is 客星 (kèxīng); the dates in square brackets are Duyvendak’s conversions.
A second record, from the court astronomers and quoted by Duyvendak from the Song huiyao, says the star was “visible by day, like Venus; pointed rays shot out from it on all sides; the color was reddish-white. Altogether it was visible for 23 days.” From the annals Duyvendak concludes that the star was visible from July 4, 1054 until April 17, 1056. We have not converted any of these dates ourselves.
In 1942 N. U. Mayall and J. H. Oort concluded that “the Crab Nebula may be identified with the 1054 supernova, which also probably was one of the brightest supernovae on record”. They name two difficulties themselves. The Crab Nebula lies about 1¼° northwest of ζ Tauri, where the record says south-east of Tianguan, but that asterism cannot be fixed more exactly than “near ζ Tauri”. And a report from Peking of a guest star in the Pleiades, seven to eight months later and some 30° away, they advise against treating it as an independent confirmation.
Su Song and his clock tower
Su Song (蘇頌 / 苏颂, Sū Sòng) was an official of the Song dynasty. His biography in the Song shi calls him a man of Nan’an in Quanzhou, courtesy name Zirong, and says he died at the age of 82, in the first year of Jianzhong Jingguo, which is 1101. It also tells how he was put in charge of making a new armillary sphere: a tower of three stories with an armillary sphere on top, a celestial globe in the middle and the time-announcers below, all joined by one mechanism that water turned, without human power (為臺三層，上設渾儀，中設渾象，下設司辰，貫以一機，激水轉輪，不假人力; our translation).
His treatise on the tower, the 新儀象法要 / 新仪象法要 (Xīn yíxiàng fǎyào), survives; an edition was printed in Shanghai in 1937 by the Commercial Press. The standard study in English is Joseph Needham, Wang Ling and Derek de Solla Price, Heavenly Clockwork (Cambridge University Press, 1960; second edition 1986, with a supplement by John H. Combridge on a modern reconstruction). The title page reproduced there reads “written by Su Sung in A D 1090”.
The first reconstruction was a model made by the archaeologist Wang Zhenduo in 1958, according to the Chinese Wikipedia; it is kept in the Chinese History Museum. About the fate of the tower itself we found only the account of the Chinese Wikipedia (see below); Heavenly Clockwork has a chapter “The fate of Su Sung’s clock in the north among the Chin Tartars”.
The Jesuits at the Beijing observatory
In China the calendar was a matter of state. The Board of Mathematics had to announce in advance, as the Catholic Encyclopedia (1913) describes it, the new and full moons, the movements of the Sun with the dates it enters each of the twenty-eight constellations of the Chinese zodiac, the solstices and equinoxes, the positions of the planets and the eclipses. In 1630 the Jesuit Johann Adam Schall von Bell (born at Cologne in 1591 according to the Catholic Encyclopedia, in 1592 according to Wikisource; died in Beijing in 1666) was called to Beijing to work on reforming the calendar. Later the Shunzhi Emperor appointed him president of the Board.
Ferdinand Verbiest was born at Pittem near Kortrijk in 1623 and died in Beijing in 1688. In 1660 he was called to Beijing to assist Schall and in the end to replace him. In the persecution of 1664 he was imprisoned, and in 1668 the emperor ordered a public test between him and a mandarin: the length of a gnomon’s shadow at noon, the positions of the Sun and the planets, and a lunar eclipse. After it Verbiest was put at the head of the Board of Mathematics. Between 1669 and 1674 he had six European-style instruments made for the observatory, which the Catholic Encyclopedia lists as a quadrant, an azimuth compass, a sextant, a celestial globe and two armillary spheres. According to a Chinese journal article by Zhang Baichun (1999) he consulted Tycho Brahe’s Astronomiae instauratae mechanica (1598) and drew on traditional Chinese visual arts; in 1674 he published the 16-volume Xinzhi lingtai yixiang zhi on the design, making and use of the instruments. The Beijing Ancient Observatory still shows his instruments on its platform.
Verbiest’s birth in Flanders is a biographical link with the Low Countries. We found no source that connects Cellarius’s Harmonia Macrocosmica (Amsterdam, 1660) with Chinese astronomy or with Chinese observations, and we make no such claim.
What we do not know
- Which text first set out the Three Enclosures as one system. The Butian ge does so, but no source we have says it was the first.
- When the Butian ge was written. Chinese Wikisource classes its author, Wang Ximing, under the Tang; Needham places him at the end of the sixth century, in the Sui.
- A fixed English name for Tàiwēi and Tiānshì. Needham describes Tàiwēi, but we have found no verified English rendering of either name, so we use pinyin.
- Whether the two lists of determinative stars agree beyond the four xiu named above. We have compared neither list with Sun and Kistemaker (1997) or with Needham’s Table 24.
- Whether the Dunhuang scroll may be shown here: the page of the International Dunhuang Project with the terms of use could not be opened.
- How the Chinese dates of the 1054 records convert to our calendar. We give Duyvendak’s conversions and have not made our own.
- What Collins, Claspy and Martin (1999) argued, in their paper on the 1054 records, against the traditional reading of them. We could not read their paper.
- When the tower and the treatise were made. The title page in Heavenly Clockwork says 1090; the Chinese Wikipedia says the tower was built from 1088 to 1092.
- What became of the tower. The Chinese Wikipedia says Jin troops took it to Yanjing (Beijing) in the disaster of 1127 and left it there in 1214; we have not read the chapter in Heavenly Clockwork that treats this and do not know whether that account is the standard one.
- The exact English names of Verbiest’s six instruments. The Catholic Encyclopedia, a Chinese journal article and the Beijing observatory each use a different list.
Related
What this page does not cover
This page is about the system and what we can calculate, with four moments from its history. The rest of that history will follow once every claim has a source. The meanings that astrologers give to the xiu belong under Astrology, and we do not give them here.
Sources
- Chinese Wikipedia, “二十八宿” (revision 95216397): the 28 xiu, the determinative stars and the Four Symbols. Read November 1, 2026.
- Chinese Wikipedia, “三垣” (revision 76484938): the Three Enclosures. Read November 1, 2026.
- English Wikipedia, “Twenty-Eight Mansions” (revision of October 1, 2026): the English names, the seasons and the second list of determinative stars, which cites Sun Xiaochun (1997), in Helaine Selin (ed.), Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures, p. 517, and the International Dunhuang Project. Read November 1, 2026. We write Dipper and Ghosts where it writes (Southern) Dipper and Ghost.
- Astronomy Engine: the Sun and the Moon, the solar terms to the minute and the positions of the determinative stars.
- Huainanzi, “Tianwen xun” (juan 3), Chinese Wikisource: the four directions with a dragon, a bird, a tiger and a tortoise; the Purple Palace and the Tàiwēi. Read November 1, 2026.
- Sima Qian, Shiji, “Tianguan shu” (juan 27), Chinese Wikisource: the four palaces of the sky; the Purple Palace, the Tàiwēi and the Tiānshì. Read November 1, 2026.
- Wang Ximing, Butian ge (Chinese Wikisource, edition of Wang Ximing, classed there under the Tang): the three enclosures and the 28 xiu under the four animals. Read November 1, 2026.
- Joseph Needham, Science and Civilisation in China, vol. 3 (Cambridge University Press, 1959): the four palaces (p. 242), Wang Hsi-Ming and the Butian ge, placed at the end of the sixth century in the Sui (p. 201), the “Purple forbidden enclosure” and the Tàiwēi enclosure. Read in the full text on the Internet Archive, November 1, 2026.
- Jean-Marc Bonnet-Bidaud, Françoise Praderie and Susan Whitfield, “The Dunhuang Chinese Sky: A Comprehensive Study of the Oldest Known Star Atlas”, Journal of Astronomical History and Heritage 12(1), 2009, pp. 39–59: the scroll, its contents, its date and its claim to be the oldest atlas. Read in the full text of the Astrophysics Data System, November 1, 2026.
- J. J. L. Duyvendak, “Further Data Bearing on the Identification of the Crab Nebula with the Supernova of 1054 A.D., Part I: The Ancient Oriental Chronicles”, Publications of the Astronomical Society of the Pacific 54, 1942, pp. 91–94: the Chinese records and their translation. Read in the page images of the Astrophysics Data System, November 1, 2026.
- N. U. Mayall and J. H. Oort, “Further Data Bearing on the Identification of the Crab Nebula with the Supernova of 1054 A.D., Part II: The Astronomical Aspects”, Publications of the Astronomical Society of the Pacific 54, 1942, pp. 95–104: the identification with the Crab Nebula and its difficulties. Read in the page images of the Astrophysics Data System, November 1, 2026.
- Song shi (History of the Song), juan 56 (treatise on astronomy, the guest star of 1054) and juan 340 (biography of Su Song), Chinese Wikisource. Read November 1, 2026.
- Joseph Needham, Wang Ling and Derek J. de Solla Price, Heavenly Clockwork: The Great Astronomical Clocks of Medieval China (Cambridge University Press, 1960; second edition 1986): the title page, the contents and the description of the supplement, as shown in the Google Books record; the 1937 edition of the Xin yixiang fayao in the record of the Ricci Institute Library. We have not read the book itself.
- Chinese Wikipedia, “水運儀象台” (the model of Wang Zhenduo, 1958, and the account of the fate of the tower). Read November 1, 2026.
- Catholic Encyclopedia (1913), “Johann Adam Schall von Bell” and “Ferdinand Verbiest”, English Wikisource; the Wikisource author page for Schall gives 1592–1666. Read November 1, 2026.
- Zhang Baichun, “The Europeanization of the astronomical instruments of the Beijing observatory in the early Qing”, Zhongguo keji shi zazhi, 1999, no. 3; abstract in Chinese and English on the CNKI portal. Read November 1, 2026.
- Visit Beijing (official), “Go to Beijing Ancient Observatory to touch sky-watching tools”: Verbiest’s instruments and the observatory platform. Read November 1, 2026.
- English Wikipedia, “Harmonia Macrocosmica”: title, author, publisher and year (Andreas Cellarius, Johannes Janssonius, Amsterdam, 1660). Read November 1, 2026.